A touch panel system in which an input operation on a touch panel is able to be performed when a user touches, with his/her finger or a touch pen, a touch panel which has a plurality of electrostatic capacitances formed at respective intersections of a plurality of first signal lines and a plurality of second signal lines is becoming pervasive. For example, in a touch panel system of a capacitive sensing method, change in an electrostatic capacitance in a touch panel, which is caused when a finger of a user or a touch pen makes contact with the touch panel, is detected, and a position at which the change in the electrostatic capacitance is caused in the touch panel is recognized as an input position to the touch panel.
Moreover, in these years, a technique relating to a touch panel system which includes, as a pen for touching a touch panel with, a stylus pen provided with a function of outputting a signal by driving a pen point is attracting attention. Furthermore, a technique for improving convenience of a user in a touch panel system by sending, for example, information indicating a writing pressure (writing pressure information), information indicating inclination of a stylus pen, or the like from the stylus pen to a touch panel is also being developed.
PTL 1 discloses a pointer (stylus pen) which performs transmission in association with a time difference between two codes of a code for detecting a position of the pointer and a code for indicating writing pressure information and a position detection apparatus which detects, from the time difference between the two codes transmitted from the pointer, a pressure applied to the pointer.
PTL 2 discloses a technique for transmitting writing pressure information by controlling an oscillation frequency of a stylus (stylus pen) in accordance with a pressure on a stylus end.